LUCIFERASE encyclopedia topics

Luciferase is a generic name for enzymes commonly used in nature for bioluminescence. The most famous one is firefly luciferase from the firefly Photinus pyralis. In luminescent reactions, light is produced by the oxidation of a luciferin (a pigment), sometimes involving adenosine triphosphate (ATP). The rates of this reaction between luciferin and oxygen are extremely slow until they are catalyzed by luciferase, often mediated by the presence of calcium ions (an analog of muscle contraction).Renilla luciferin reaction is triggered by calcium ions. (cited September 6, 2006) The reaction takes place in two steps:

luciferin + ATP → luciferyl adenylate + PP_i

luciferyl adenylate + O₂ → oxyluciferin + AMP + light

The reaction is very energy efficient: nearly all of the energy input into the reaction is transformed into light. As a comparison, the incandescent light bulb loses about 90% of its energy to heat.

Luciferin and luciferase are not specific molecules. They are generic terms for a substrate and its associated enzyme (or protein) that catalyze a light-producing reaction. A variety of organisms regulate their light production using different luciferases in a variety of light-emitting reactions. The most famous are the fireflies, although the enzyme exists in organisms as different as the Jack-O-Lantern mushroom (Omphalotus olearius) and many marine creatures. In fireflies, the oxygen required is supplied through a tube in the abdomen called the abdominal trachea. The luciferases of fireflies - of which there are over 2000 species - and of the Elateroidea (fireflies, click beetles and relatives) in general - are diverse enough to be useful in molecular phylogeny. The most thoroughly studied luciferase is that of the Photinini firefly Photinus pyralis, which has an optimum pH of 7.8.

Applications

Luciferase can be produced in the lab through genetic engineering for a number of purposes. Luciferase genes can be synthesized and inserted into organisms or transfected into cells. Mice, silkworms, and potatoes are just a few organisms that have already been engineered to produce the protein.

In the luciferase reaction, light is emitted when luciferase acts on the appropriate luciferin substrate. Photon emission can be detected by light sensitive apparatus such as a luminometer or modified optical microscopes. This allows observation of biological processes.

In biological research, luciferase commonly is used as a reporter to assess the transcriptional activity in cells that are transfected with a genetic construct containing the luciferase gene under the control of a promoter of interest. Luciferase can also be used detect the level of cellular ATP in cell viability assays or for kinase activity assays. Additionally proluminescent molecules that are converted to luciferin upon activity of a particular enzyme can be used to detect enzyme activity in coupled or two-step luciferase assays. Such substrates have been used to detect caspase activity and cytochrome P450 activity, among others.

Whole animal imaging (referred to as in vivo or, occasionally, ex vivo imaging) is a powerful technique for studying cell populations in live animals, such as mice. Different types of cells (e.g. bone marrow stem cells, T-cells) can be engineered to express a luciferase allowing their non-invasive visualization inside a live animal using a sensitive CCD camera.This technique has been used to follow tumorigenesis and response of tumors to treatment in animal models. Luciferase can be used in blood banks to determine if red blood cells are starting to break down. Forensic investigators can use a dilute solution containing the enzyme to uncover traces of blood remaining on surfaces at a crime scene. Luciferase is a heat sensitive protein that is used in studies on protein denaturation, testing the protective capacities of heat shock proteins. The opportunities for using luciferase continue to expand.

References

External links

Baldwin TO (1996). "Firefly luciferase: the structure is known, but the mystery remains". Structure 4 (3): 223–8.
Greer LF, Szalay AA (2002). "Imaging of light emission from the expression of luciferases in living cells and organisms: a review". Luminescence 17 (1): 43–74.
Trimmer B, Zayas R, Qazi S, Lewis S, Michel T, Dudzinski D, Aprille J, Lagace C Firefly flashes and Nitric Oxide. Tufts University. Retrieved on 2008-10-02..
Crystallographic structures: ,
Trends in development of reporter genes. Reporter Genes. Retrieved on 2008-10-02..
Chemistry of Bioluminescence. BL Web. Retrieved on 2008-10-02..
Promega Gene Expression and Reporter technologies using Luciferase
Promega Protocols and Applications Guide: Bioluminescence Reporters